MEMS (Micro-Electro-Mechanical Systems) sensors are highly popular in markets requiring the measurement of motion, acceleration, tilt, and vibration. As system-in-package solutions, MEMS sensors offer numerous advantages, including high resolution, low power consumption, and compact size. MEMS differ fundamentally from semiconductor chips that primarily utilize the electrical properties of silicon. Instead of featuring gate, drain, and source terminals, the core component of a MEMS device is a micromachined mechanical structure made entirely of silicon. A typical MEMS structure comprises a proof mass (slider), springs, and dampers, operating on principles essentially identical to a mass-spring model. MEMS sensors enable intuitive human-machine interfaces for devices such as mobile phones, MP3/MP4 players, PDAs, and game controllers, allowing user movements to interact with the equipped device.
In home appliances like washing machines or dryers, MEMS accelerometers can function as vibration detectors; if the load becomes unbalanced, the machine alerts the user, thereby preventing premature wear or damage caused by the imbalance. Single-axis and dual-axis accelerometers are widely used in automotive passive safety systems, such as frontal and side airbags. Accelerometers and gyroscopes are also employed in navigation and active safety systems, including ABS (Anti-lock Braking Systems) and dynamic stability control systems.
In recent years, MEMS sensors have seen a trend toward "consumerization," penetrating the consumer electronics market to address a variety of application needs. Consumer electronics manufacturers are seeking MEMS sensors that are miniature, low-cost, low-voltage, and energy-efficient. Slim designs are the prevailing trend for battery-powered products such as mobile phones, MP3/MP4 players, and portable PCs. Furthermore, multi-axis sensors have become a standard feature in consumer electronics, enabling users to activate functions regardless of the device's physical orientation. However, there is currently no fixed reference framework for MEMS sensor applications in portable products.
Additionally, as the product lifecycles of consumer electronics continue to shorten, designers require MEMS sensors that can be rapidly and seamlessly integrated into end-user applications. At the forefront of MEMS technology development, STMicroelectronics has begun integrating multiple sensors—accelerometers, gyroscopes, and magnetometers—into a single package; this solution enhances the functionality and performance of various applications, including motion monitoring. Integrated sensors enable autonomous and automated systems to monitor specific conditions and translate them into actions with little to no user intervention. In portable mobile devices such as mobile phones, game consoles, and personal navigation systems, a sensor capable of precisely measuring angular rate across three orthogonal axes enables 360° angular rate detection and high-precision recognition of 3D gestures and movements. Furthermore, combining a 3-axis accelerometer with a gyroscope allows designers to develop inertial measurement units (IMUs) that track the motion type, speed, and direction of humans, vehicles, and other objects, providing comprehensive data. STMicroelectronics' accelerometers feature a range of enhanced capabilities, including single- and double-tap recognition, motion detection/wake-up functions, and 4D/6D orientation detection. Other key features include a programmable FIFO (First-In-First-Out) buffer and two programmable interrupt output pins, enabling immediate notification of the host processor regarding events such as motion detection or tap actions.
Integrating compass modules into mobile phones has sparked an application revolution in the mobile market by enabling advanced location-based services. With both compass and GPS capabilities, consumers can simply point their phones at nearby facilities—such as hotels or shopping malls—to identify and search for information about those locations.
Combining motion detection with magnetic sensing significantly improves the user experience in various ways. Application developers can effectively address the challenges of viewing maps on devices with limited screen sizes, such as mobile phones or PDAs; by positioning the user's current location at the bottom of the map and displaying the direction of travel at the top, the system provides accurate navigational guidance. This setup indicates the direction of travel for a person or vehicle even when GPS signals are unavailable. The solution also supports dead-reckoning applications, facilitating pedestrian navigation in areas with no or weak GPS signals—such as inside high-rise buildings or in dense, mountainous terrain.
STMicroelectronics has integrated a 3-axis digital accelerometer and a 3-axis digital magnetometer into its LSM303DLH module. This digital compass offers a combination of high precision, compact size, and low power consumption, meeting the market's growing demand for advanced navigation capabilities and emerging smart location-based services. STMicroelectronics' high-performance System-in-Package (SiP) digital compass utilizes Honeywell's magnetoresistive technology to facilitate the integration of enhanced electronic compass functions—such as heading detection, map/display orientation, location-based services, and pedestrian dead reckoning—into portable consumer electronics. The device features user-selectable ranges for linear acceleration (±2/±4/±8g) and magnetic field strength (±1.3 to ±8 Gauss).
Many technical and business experts view wireless sensor networks, home robotics, smart pills, and lab-on-a-chip devices as the next major commercial opportunities for MEMS sensors. Examples include lab-on-a-chip technology for personalized drug development and tire pressure monitoring systems based on five-node wireless pressure sensor networks. STMicroelectronics' MEMS experts are currently focused on developing "smart sensors." These devices integrate MEMS components and a processor within a single package, enabling them to execute sensor algorithms independently without host processor intervention. This capability reduces system-level power consumption—a critical factor for power-hungry handheld devices.
